1. Field
The present disclosure relates generally to aircraft and, in particular, to composite structures for aircraft. Still more particularly, the present disclosure relates to a method and apparatus for installing a bushing and a fastener in a composite structure used in aircraft.
2. Background
Aircraft are being designed and manufactured with greater and greater percentages of composite materials. Composite materials are used in aircraft to decrease the weight of the aircraft. This decreased weight improves performance features such as payload capacities and fuel efficiencies. Further, composite materials provide longer service life for various components in an aircraft.
Composite materials are created by combining two or more functional components. For example, a composite material may include reinforcing fibers bound in a polymer resin matrix. The fibers may be unidirectional or may take the form of a woven cloth or fabric. The fibers and resins are arranged and cured to form a composite material.
In manufacturing composite structures, layers of composite material are typically laid up on a tool. The layers may be comprised of fibers in sheets. These sheets may take the form of fabrics, tape, tows, or other suitable forms. In some cases, resin may be infused or preimpregnated into the sheets. These types of sheets are commonly referred to as prepreg.
The different layers of prepreg are laid up in different orientations and different numbers of layers may be used depending on the thickness of the composite structure being manufactured. These layers may be laid up by hand or by using automated lamination equipment such as a tape laminating machine or a fiber placement system. After the different layers of composite material have been laid up on the tool, the layers of composite material may be consolidated and cured upon exposure to temperature and pressure, thus forming the final composite structure.
In some cases, inconsistencies may occur in composite structures during various stages of manufacturing and use. For example, inconsistencies in an aircraft composite structure may occur during manufacturing, transport, maintenance, in-service, or other stages of use. Examples of inconsistencies that may be present in a composite structure include voids, porosity, delamination, foreign object debris (FOD), an incorrectly drilled hole, cracks, and other types of inconsistencies.
These inconsistencies may occur in various parts of the composite structure. For example, delamination may occur near a fastener hole drilled in the composite structure. This delamination may be caused when one layer of composite material separates from another layer when the resin bonding the layers does not perform as desired. In another illustrative example, tooling of the composite structure may cause inconsistencies.
When inconsistencies are present, composite structures often need rework. The rework may include repair, replacement, or some combination thereof. For example, a portion of the composite structure may be replaced with a patch. In still other examples, a plug may be used to rework a fastener hole in the composite structure. In still other instances, the composite structure may be discarded and replaced with a new composite structure.
This rework reduces the availability of aircraft carrying passengers, cargo, or other items. These effects may be more costly and time-consuming than desired. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.